The invention relates to a rotary slide valve having a cylindrical rotary plug mounted rotatably in a stationary housing with a passage of circular cross section for the connection of three connection lines, the circular cross sections of the three connection lines and the cross section of the passage of the rotary plug being approximately equal in all passage positions of the rotary slide valve.
A rotary slide valve of the generic type is known, for example, from German Offenlegungsschrift 3,730,419. This three-way rotary slide has a cylindrical rotary plug which is mounted via the center of its two end faces rotatably in a rotary slide housing. The rotary slide valve serves for the connection of a first and second connection line, aligned with each other, and--on rotation of the rotary plug--for the connection of a third connection line branching off at an angle from the first connection line. Here, in the case of branching off at an angle the circular cross section of the first connection line and the circular cross section of the rotary plug passage bore hole adjoining it are not of congruent construction (i.e., in this valve position a change in the conveying cross section occurs at this point). As a result of this construction, passage through the valve is not possible without jolting.
A rotary slide valve of similar construction is known from German Utility Model GM 8,811,639.
In all these and also other known rotary slide valve, the cylindrical rotary plug is located in a correspondingly adapted cylindrical housing. The passage bore hole through the rotary plug is of straight-line construction and should as far as possible have the same round diameter as the different connection lines in order to avoid a change in cross section.
As can be seen from the abovementioned publications, the transition between the individual connection lines to the rotary plug takes place on the cylinder envelope surface formed by the rotary plug. In the case of the aligned, straight-line passage from the first to the second connection lines, there are no adaptation problems of the transition cross sections. However, as already mentioned, this does not apply for the position in which the rotary plug is set for branching off at an angle. Here, the difficulty or disadvantage which always results is that the branching connection cross section, lying on the cylinder envelope surface of the rotary plug, of the passage bore hole in the rotary plug does not correspond exactly or is not congruent with the connection cross section of the first connection line in the rotary slide housing. It is therefore necessary for these connection lines to be slightly padded in their lateral region in the housing in order to obtain a passage through the rotary slide valve without jolting, at least in one conveying direction. If the rotary plug is then again turned in the straight-line passage direction, the padding may no longer be necessary. Thus, it is responsible for a disadvantage in that rotary slide valve passage without jolting is now only possible in one conveying direction. A further disadvantage is that there is a restriction in the cross section in the region of the padding.